Technical Field
The present disclosure relates to a position indicator which includes a resonance circuit configured from at least an inductance element and a capacitance element and used together with a position detection apparatus.
Description of the Related Art
As a position detection method of an electromagnetic induction type, a method is used conventionally in which an alternating current (AC) signal (radio wave) is transferred between a position detection apparatus (tablet) and a position indicator and coordinate values of an indication position on a sensor of the position detection apparatus by the position indicator can be detected by the position detection apparatus (for example, refer to Patent Document 1 (Japanese Patent Laid-Open No. 1988-70326)).
In the position detection apparatus of Patent Document 1, a radio wave of a predetermined frequency is transmitted from a loop coil of the sensor and received by a resonance circuit provided in the position indicator. Then, the loop coil of the sensor is changed over into a reception state such that a radio wave transmitted from the resonance circuit of the position indicator by which the radio wave has been received is received by the loop coil to generate an induction voltage. Then, the processes described above are repetitively executed successively changing over the loop coil among a plurality of loop coils of the sensor, and coordinate values of an indication position by the position indicator are calculated on the basis of the level of the induction voltage generated on each loop coil.
In a conventional position indicator used for such a position detection method of the electromagnetic induction type as described above, a variable capacitor whose capacitance continuously varies in response to a writing pressure applied to a core member of the position indicator is used as part of capacitors which configure resonance circuits each configured from a parallel connection of a coil as an example of an inductance element and a capacitor as an example of a capacitance element. On the other hand, a continuous variation of a resonance frequency (or a continuous variation of a phase angle) is detected from the induction voltage received from the resonance circuit of the position indicator by the position detection apparatus to obtain information according to the writing pressure applied to the core member described above (refer to, for example, Patent Document 2 (Japanese Patent Laid-Open No. 2010-129920)).